The following abbreviations employed herein are defined as follows:
AMR Adaptive Multi-Rate
BSS Base-Station Subsystem
DTX Discontinuous transmission
FACCH Fast Associated Control Channel
FR Full Rate
GERAN GSM/EDGE Radio Access Network
GPRS General Packet Radio System
HR Half Rate
PC Power Control
PDTCH Packet Data Traffic Channel
SACCH Slow Associated Control Channel
SI System Information
TA Timing Advance
TSG-GERAN Technical Specification Group GERAN
UI Un-numbered Information
WB Wideband
It has been generally accepted within TSG-GERAN that the link performance of the associated control channels (FACCH & SACCH) is a limitation to realizing the full capacity gains that are achievable with AMR coding.
The inventors are aware of two proposals have been made within TSG-GERAN to enhance the operation of the SACCH.
The first proposal, denoted ‘Parallel SACCH’, proposes to send a SACCH repetition within IDLE slots of a traffic channel. This would then allow the mobile station to combine the SACCH and the parallel SACCH sent using the IDLE slot(s) of a traffic channel prior to decoding, thus improving the likelihood of a successful decode.
One drawback of this approach is that the IDLE slots are already used by the mobile station to perform neighbor cell monitoring, and reducing the time available for neighbor cell monitoring would have an adverse impact on handover performance. To provide the possibility of an early decode, it was proposed to reverse the order that the parallel SACCH blocks are sent. However, it is unclear if this would provide a benefit in poor channel conditions, when the need to receive all parallel SACCH blocks will be the greatest.
The second proposal, denoted ‘Spread SACCH’, proposes to send a SACCH repetition through the use of speech bit stealing. However, this approach would adversely impact speech quality, and is not compatible with DTX. In addition, a different speech puncturing pattern would be needed on a per mode, per traffic channel basis, implying a complex solution. Currently, the following traffic channels require an enhancement: AMR FR, E-AMR HR, AMR-WB FR, E-AMR-WB FR & E-AMR-WB HR (on these channels the code rate of the most robust mode is significantly less than the SACCH).
What is thus needed, and what was not available prior to this invention, is a satisfactory procedure to eliminate the above-described and other limitations with regard to the SACCH channel.